vmdk: fix VMFS extent parsing

The VMFS extent line in description file doesn't have start offset as
FLAT lines does, and it should be defaulted to 0. The flat_offset
variable is initialized to -1, so we need to set it in this case.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/vmdk.c

@@ -726,6 +726,8 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
                 error_setg(errp, "Invalid extent lines: \n%s", p);
                 return -EINVAL;
             }
+        } else if (!strcmp(type, "VMFS")) {
+            flat_offset = 0;
         } else if (ret != 4) {
             error_setg(errp, "Invalid extent lines: \n%s", p);
             return -EINVAL;